整合MyBatisPlus操作数据库

整合MyBatisPlus操作数据库

1、什么是MyBatis-Plus

MyBatis-Plus（简称 MP）是一个 MyBatis 的增强工具，在 MyBatis 的基础上只做增强不做
改变，为简化开发、提高效率而生。

mybatis plus 官网

IDEA的MyBatis的插件 - MyBatisX

优点

只需要我们的Mapper继承 BaseMapper 就可以拥有crud能力

CREATE TABLE user
(
	id BIGINT(20) NOT NULL COMMENT '主键ID',
	name VARCHAR(30) NULL DEFAULT NULL COMMENT '姓名',
	age INT(11) NULL DEFAULT NULL COMMENT '年龄',
	email VARCHAR(50) NULL DEFAULT NULL COMMENT '邮箱',
	PRIMARY KEY (id)
);

INSERT INTO user (id, name, age, email) VALUES
(1, 'Jone', 18, '[email protected]'),
(2, 'Jack', 20, '[email protected]'),
(3, 'Tom', 28, '[email protected]'),
(4, 'Sandy', 21, '[email protected]'),
(5, 'Billie', 24, '[email protected]');

        <dependency>
            <groupId>com.baomidou</groupId>
            <artifactId>mybatis-plus-boot-starter</artifactId>
            <version>3.4.1</version>
        </dependency>

编写实体类

@AllArgsConstructor
@NoArgsConstructor
@Data
public class User {
    
    
	
	//下面两个不是数据库字段，所以采用注解方式注释掉
  	@TableField(exist = false)
    private String username;
    @TableField(exist = false)
    private String password;

    //下面是数据库字段
    private Long id;
    private String name;
    private Integer age;
    private String email;
}

编写UserMapper

@Mapper
public interface UserMapper extends BaseMapper<User> {
    
    

}

测试

	@Autowired
    UserMapper userMapper;
    
    @Test
    void testUserMapper(){
    
    
        User user = userMapper.selectById(1L);
        log.info("用户信息{}",user);
    }

数据列表展示

使用MyBatis Plus提供的IService，ServiceImpl，减轻Service层开发工作。

public interface UserService extends IService<User> {
    
    
}

@Service
public class UserServiceImpl extends ServiceImpl<UserMapper, User> implements UserService {
    
    

}

Controller

	@Autowired
    UserService userService;
	@GetMapping("/dynamic_table.html")
    public String dynamic_table(Model model) {
    
    
        //从数据库中查出user表中的用户进行展示
        List<User> list = userService.list();
        model.addAttribute("users",list);
        return "table/dynamic_table";
    }

 <tbody>
        <tr class="gradeX" th:each="user,stats:${users}">
            <td th:text="${stats.count}">Trident</td>
            <td th:text="${user.id}">id</td>
            <td th:text="${user.name}">Internet
                Explorer 4.0</td>
            <td th:text="${user.age}">Win 95+</td>
            <td class="center hidden-phone">[[${
    
    user.email}]]</td>
            <td class="center hidden-phone">X</td>
        </tr>
        </tbody>

实现分页功能

@GetMapping("/dynamic_table.html")
    public String dynamic_table(@RequestParam(value = "pn",defaultValue = "1")Integer pn,
                                Model model) {
    
    
        //分页查询数据
        Page<User> userpage = new Page<>(pn, 2);
        //分页查询的结果
        Page<User> page = userService.page(userpage, null);
        long current = page.getCurrent();//代表当前第几页
        long pages = page.getPages();//当前分页总页数
        long total = page.getTotal();//列表
        List<User> records = page.getRecords();

        model.addAttribute("users",page);
        return "table/dynamic_table";
    }

<table class="display table table-bordered table-striped" id="dynamic-table">
    <thead>
        <tr>
             <th>#</th>
             <th>id</th>
             <th>name</th>
             <th>age</th>
             <th>email</th>
             <th>操作</th>
        </tr>
    </thead>
    <tbody>
        <tr class="gradeX" th:each="user: ${users.records}">
            <td th:text="${user.id}"></td>
            <td>[[${user.name}]]</td>
            <td th:text="${user.age}">Win 95+</td>
            <td th:text="${user.email}">4</td>
            <td>
                <a th:href="@{/user/delete/{id}(id=${user.id},pn=${users.current})}" 
                   class="btn btn-danger btn-sm" type="button">删除</a>
            </td>
        </tr>
    </tfoot>
</table>

<div class="row-fluid">
    <div class="span6">
        <div class="dataTables_info" id="dynamic-table_info">
            当前第[[${users.current}]]页  总计 [[${users.pages}]]页 
             共[[${users.total}]]条记录
        </div>
    </div>
    <div class="span6">
        <div class="dataTables_paginate paging_bootstrap pagination">
            <ul>
               <li class=""><a th:href="@{/dynamic_table.html(pn=${users.current-1})}">←
                                                    前一页</a></li>
                <li th:class="${num == users.current?'active':''}" 
                    th:each="num:${#numbers.sequence(1,users.pages)}" >
                    <a th:href="@{/dynamic_table(pn=${num})}">[[${num}]]</a>
                </li>
                <li class=""><a th:href="@{/dynamic_table.html(pn=${users.current+1})}">
                下一页→ </a></li>
            </ul>
        </div>
    </div>
</div>

实现删除用户

@GetMapping("/user/delete/{id}")
    public String deleteUser(@PathVariable("id") Long id,
                             @RequestParam(value="pn",defaultValue = "1")Integer pn,
                             RedirectAttributes ra){
    
    

        userService.removeById(id);
        ra.addAttribute("pn",pn);
        return "redirect:/dynamic_table.html";
    }

 <td>
		<a th:href="@{/user/delete/{id}(id=${user.id},pn=${users.current})}"
		class="btn btn-danger btn-sm">删除</a>
</td>